The invention relates to devices for the low-temperature storage (in particular cryostorage, cryopreservation) of suspension samples, in particular a cryostorage device for suspended biological cells, cell groups, or cell components, and methods for low-temperature storage.
The cryostorage of biological samples has numerous applications that are aimed at a continuous storing of the samples while maintaining their vitality state. The devices used for cryostorage are adapted to the particular samples and the requirements during sample handling. In transplantation medicine, for example, organs or organ parts may be stored at low temperatures. In transfusion medicine, blood donations are stored in the deep-frozen state in blood banks.
In conventional applications of cryostorage, frequently the point is to accommodate the largest possible sample volumes in the narrowest possible space. For example, blood donations are kept in blood bags or blood tubes that may be densely packed in the blood bank. The blood bags are provided with a labeling (e.g. bar code) in order to allow for a selective and error-free removal from the blood bank. This conventional cryostorage is limited to use with large samples (ml to l range). However, in cell biology and in molecular biotechnology, the task exists to store and, if necessary, process biological samples of minimal size (single cells, cell groups, or cell components) in the deep frozen state.
In EP 804 073, for example, the cryoprocessing of individual cells is described. Cells are fixed on a substrate in the deep frozen state, stored and, if necessary, processed. This technique has the disadvantage that the storing of the cells that are fixed on substrates may be relatively space-consuming, so that the assembly of a cryo cell bank is complicated. Furthermore, in order to avoid contaminations of cryo-fixed cells, the substrates that are loaded with the samples have to be provided with a protective layer. The handling of the samples stored in such a manner is thereby complicated.
It is described in DE 199 21 236 to deposit drop-shaped suspension samples for cryopreservation on structured substrates, with the help of which the handleability of the frozen samples is facilitated. As carriers of the samples the substrates possess sample receptacles in the form of recesses, the size of which is adapted to the drop volume. The structured substrates may feature matrix-like arranged sample receptacles, as known from micro- or nanotiter plates. Theses cryo-substrates have disadvantages with respect to sample loading and sample withdrawal. For sample loading, all sample receptacles have to be filled by means of a dispensing device. This can be very time-consuming with use of single dispensers. When a multiplicity of parallel working dispensers is used, their geometric arrangement has to be adapted to the cryo-substrate. For sample withdrawal, the drop that is stored in a sample receptacle has to be completely thawed, even if only a part of the drop is needed.
In U.S. Pat. No. 4,262,494, a cryostorage device with a plurality of capillary sample chambers that are arranged in a portable cooling container is described. The sample chambers are arranged protruding from a wall of the cooling container with spacing between them. This cryostorage device is optimized specifically for the transport of cryo-samples. It has disadvantages with respect to the loading of the rigidly formed sample chambers and the long-term storage under cryo-conditions.
A cryostorage device with at least one tubular or pillow-shaped sample chamber that is attached to a data storage is known from WO 02/46719. The attachment is made directly or with a holding frame on an encapsulation of the data storage. With this technique it may be disadvantageous that an auxiliary device may be required for loading of the sample chamber. In addition, the size and thereby the load capacity of the sample chamber is limited by the dimensioning of the data storage. Capillary sample chambers for cryostorage are also described in WO 99/20104. The sample chambers are embedded in a cooling body, which results in the same disadvantages as with the technique according to WO 02/46719.
It is the object of the invention to provide an improved cryostorage device, with the help of which the disadvantages of conventional cryostorage devices are overcome and which in particular allows for a simplified loading with a multiplicity of suspended cells, cell groups, or cell components within short periods of time and which allows for a selective, partial withdrawal of sample components. In particular, the cryostorage device should also allow for the recording and reading of data that belong to each stored sample. It is also the object of the invention to provide an improved method for cryostorage.